SPH results. Top: surface density of gas and 1 mm dust grains after t = 50 T_orb. The positionsof the planets are shown as red dots in the left panel. Bottom: temporal evolution of the azimuthally averaged surface density profiles. The final positions of the two planets are indicated by the vertical dashed lines. The shape of the outer gap, both in gas and in dust, reflect the radial migration of the planet.